(a) Field of the Invention
The present invention relates to an agricultural water-recycling system comprising an iron (Fe)-ionizing module and a method for recycling agricultural water using the same, and more particularly to an agricultural water-recycling system comprising an iron (Fe)-ionizing module and a method for recycling agricultural water using the same, in which phosphorus (P) contained in effluent from a sewage treatment plant is removed by using the iron (Fe)-ionizing module including: an iron (Fe)-ionizing electrode consisting of an iron plate serving as a cathode and a titanium plate serving as an anode; and an electrode-washing device.
(b) Background of the Related Art
Recently, most lakes in Korea suffer from a water bloom of cyanobacteria and aggravation of water quality due to their sharp eutrophication caused in the second half of the 1980s. In particular, since farm lands and livestock farmhouses are located near the banks of all the lakes except some of small reservoirs in the mountainous regions where people don't dwell, a large amount of phosphorus is leaked enough to eutrophicate the lakes.
As a result of comparison between the generation sources of phosphorus in Korea, it is estimated that the largest amount of phosphorus is generated from a fertilizer, and an extraordinarily larger amount of phosphorus is generated from livestock than human beings. Particularly, it is reported that fertilizers and livestock excretions are main supply sources of phosphorus in the upper and middle stream areas of the lakes where a great city does not exist on their basins. The fact that the livestock becomes a main supply source of phosphorus means that since Korean Livestock Industry mostly depends upon imported animal feedstuffs, a large amount of nutrient salt is introduced externally into the basin of the lake. The livestock excretions possess the characteristics of a non-point source in that they are spread as composts over the farm lands, and then are leaked into the lake during a heavy rain fall. Thus, the main cause of eutrophication of reservoirs in Korea can be considered to be fertilizers and livestock excretions.
Since the basin of Lake Soyang is sparsely populated and has no industrial activity, contribution of point source pollution is small, and small-scaled point source pollutions are scattered with taking the characteristics of a non-point source pollution or take a form of area source pollution. This can be considered to be a typical form of a reservoir situated at the upper stream of the river in Korea, and the inflowing pattern of a non-point source pollution in the Lake Soyang basin is exemplary in Korean lakes.
The discharge rate of rivers in Korea greatly varies seasonally depending on the rainfall. In the case where a heavy downpour does not fall, the flow rate of effluent discharged from the river basin is very small, resulting in a considerable decrease in contribution to annual loads. Since there was no large rainfall during the period from 1991 to 1994, the flow rate of effluent from the river basin was small. A heavy rain whose precipitation is 100 mm fell in July 1995 after several years of drought, so that an initial effluent of the rain contained higher concentration pollutants.
Phosphorus discharged from a non-point source pollution resulting from agricultural activities occupies the majority of the entire phosphorus loads on the basins of large-scale dams in Korean. Therefore, all the attempts to prevent eutrophication of the lakes must be focused on the management of a non-point source pollution including fertilizers, livestock excretions and the like as well as the sewage treatment.
It is considered that the fertilizers and livestock excretions are an important contamination source of the river basin. Thus, a system for collecting and treating the fertilizers and livestock excretions is regarded as a target which must be invested most preferentially so as to improve water quality, and will be a secure alternative which is the most effective as an investment for improvement of water quality. Since it is nearly impossible for small-scale farmhouses to collect and treat livestock excretions, the central government and a local government must support the collection of the night soil and the construction of a night soil treatment plant. This will exhibit effects of reducing a burden for the treatment of livestock excretions of farmhouses, and simultaneously alleviating a damage burden of water quality pollution of the lower stream of the river.
A technology which has been developed so far to purify the water quality is largely classified into a chemical treatment process, a biological treatment process, a physical treatment process and an electrolytic process which has been recently developed.
As a representative technology of the electrolytic process, there is proposed a agricultural wastewater treatment method using electrolysis characterized in that wastewater is treated by means of electrochemical oxidation and electrofloatation using an iron or aluminum electrode (Korean Patent Registration No. 533,246). However, such a agricultural wastewater treatment method has an inconvenience of having to separately performing a step of alternately reversing the polarities of a pair of electrodes made of iron (Fe) or aluminum (Al) for operation and a step of washing a contaminated electrode.
The present inventor has also developed a wastewater treatment system using an iron precipitation reactor adopting an electrolysis method (Korean Patent Registration No. 787,122). However, such a wastewater treatment system still entails a drawback in that polarities of electrodes must be switched arbitrarily and the problem of electrode pollution is not resolved.